DFT study and electrochemical investigation of Fe3+ion interaction on chalcopyrite (001)-S and M (M = Cu, Fe) surfaces: A thermodynamic insights

Highlight• Increase in intensity of the anodic and cathodic peaks in the presence of Fe³⁺ ion. • Columbic Interaction between Fe³⁺ ion on (0 0 1)-S and (0 0 1)-M surfaces. • Spontaneous reaction with free energy −87 and −82 kJ/mol for (0 0 1)-S and (0 0 1)-M. Ferric sulfate is a common oxidant of chalcopyrite leaching in an acidic medium, and the oxidation of chalcopyrite in the presence of ferric (Fe³⁺) ion increases copper extraction. In this work, the effect of ferric ion on chalcopyrite leaching is investigated by electrochemical analysis (cyclic voltammetry and linear sweep voltammetry methods) and density functional theory study. According to the cyclic voltammetry data, the presence of ferric ion showed the positive effect on the anodic and cathodic reactions to reduce the non-faraday region. Moreover, the Tafel plots revealed that the inactive region was removed by the presence of ferric ion with increasing corrosion current density. The reaction free energy value, resulting in the density of corrosion current, was related to the coulombic reaction of electroactive species (Fe³⁺ ion) with the surface. Subsequently, Fe³⁺ ion interaction with the (0 0 1)-S and (0 0 1)-M surfaces (M = Fe and Cu) of chalcopyrite was studied by using the density functional theory calculations. The computational data indicated that the Fe³⁺ ion interaction on chalcopyrite surfaces was favorable. In order, the presence of sulfur atoms decreased the coordination of the surface cations lead to more reactivity of surfaces. Thermodynamic data from computational and electrochemical studies showed that the interaction of Fe³⁺ ion with surfaces of chalcopyrite is a spontaneous reaction. The value of free energy for the ferric ion interaction in the presence of pyrite was obtained −17/8 kJ/nonindicated positive effect of pyrite on the reaction with increasing the reduction rate of Fe³⁺ ion.